A communication system can be seen as a facility that enables communication sessions between two or more entities such as user equipment and/or other nodes associated with the communication system. The communication may comprise, for example, communication of voice, data, multimedia and the like. A session may, for example, be a telephone call type session between users, a multi-way conference session, or a communication session between user equipment and an application server (AS) such as a service provider server.
A communication system typically operates in accordance with a given standard or specification which sets out what the various entities associated with the communication system are permitted to do and how that should be achieved. For example, the standard or specification may define if the user, or more precisely, user equipment is provided with a circuit switched service and/or a packet switched service. Communication protocols and/or parameters which shall be used for the connection may also be defined. In other words, a specific set of rules on which the communication can be based is defined to enable communication.
Communication systems providing wireless communication for user equipment are known. An example of a wireless system is the public land mobile network (PLMN). PLMNs are commonly based on cellular technology. In cellular systems, a base transceiver station (BTS) or similar access entity services mobile user equipment (UE) via a wireless interface between these entities. The communication on the wireless interface between the user equipment and elements of the communication network can be based on an appropriate communication protocol. The operation of the base station apparatus and other apparatus required for the communication can be controlled by one or several control entities. The various control entities may be interconnected.
One or more gateway nodes may be provided for connecting the cellular access network to other networks, for example to a public switched telephone network (PSTN) and/or other communication networks such as an IP (Internet Protocol) and/or other packet switched data networks. In such arrangements, the mobile communications network provides an access network enabling a user with wireless user equipment to access external networks, hosts, or services offered by specific service providers.
An example of the type of services that may be offered to a user such as a subscriber to a communication system is the so called multimedia service. Some of the communication systems enabled to offer multimedia services are known as internet protocol multimedia networks. IP multimedia functionalities can be provided by means of an IP multimedia core network subsystem (IMS). The IMS includes various network entities for the provision of multimedia services. IMS services are intended to offer, amongst other services, IP based packet data communication sessions between mobile user equipment.
In a packet data network, a packet data carrier may be established to carry traffic flows over the network. An example of such a packet data carrier is a packet data protocol (PDP) context.
Various types of services are provided by means of different application servers (AS) over IMS. Some of these services may be time critical. An example of a time critical service that may be provided over the IMS is the so-called direct voice communication service. One example of this type of service is the ‘push-to-talk over cellular’ (PoC) service also known as the PTT (push-to-talk service). The direct voice communication services are intended to use the capabilities of the IMS to enable IP connections for user equipment and other parties to the communication, such as other user equipment or entities associated with the network. The service allows users to engage in immediate communication with one or more users.
The principle behind push-to-talk over cellular (PoC) communication systems is one where the capabilities of a walkie-talkie system are implemented within a standard cellular phone. Users simply select the person or groups of persons they wish to talk to from their phone and press the push to talk key on their mobile phone to start talking. The activation may be via a specific button, tangent or any other appropriate key of the keyboard. Similar principals apply with devices having touch sensitive or sound activated user interfaces. While the user speaks, the other user or users may listen. Bi-directional communication may be offered since all parties of the communication session may similarly communicate voice data with the PoC application server. Turns to speak are requested by activating the push to talk button or the like. The response time of connection is almost instantaneous.
Push-to-talk calls are typically half-duplex communications, i.e. while one user speaks the others listen. The turn to speak is granted by pressing the push-to-talk key on a first come first served basis or based on priorities. Push-to-talk calls are usually connected without the recipient answering and typically received through the phone's built in loud speaker.
As this system is integrated within the cellular telecommunication system this provides a coverage area greater than that provided using traditional two-way radio systems. The push-to-talk service may be implemented using push-to-talk servers in a IP multimedia subsystem (IMS) system. The push to talk service is based on multi-unicasting. Each transmitting handset sends packet data traffic to a dedicated push-to-talk server (a participating server). A controlling server receives the traffic and manages the shared floor for a group call. The controlling server duplicates the traffic to be received by all recipients. No multi-casting is performed either in the GPRS access network or over the radio access network.
The push to talk over cellular telecommunication system such as described within the push to talk over cellular draft provisions such as the ‘OMA Push to talk over Cellular (PoC)-Architecture’.
Groups of communicating user equipment using the PoC system can be created in various ways. The Internet Engineering Task Force (IETF) defines one such system using session initiation protocol (SIP) or Conference Policy Control Protocol (CPCP). Voice and data control traffic once the groups are set up is carried through a real time protocol (RTP) streaming bearer. The PoC system uses transport protocols based on those described in IETF RFC 3550. The RTP protocol describes the architecture of the data packets and the syntax of the data stored within the packets passing the voice and data information from user to user.
The issue of privacy and anonymity over a PoC network has not been addressed. A user of a PoC network may wish to send a message and withhold their identity from the final destination whilst still being able to communicate an identity to one or more intermediaries.
Although there exists some SIP protocols for example ITEF RFC 3323 and ITEF RFC 3325 which enable users to withhold their identity whilst setting up an IMS connection there has been no discussion of how the data in a PoC network maintains the user's anonymity.
Furthermore there is no method available to enable a user, having joined a group, to request to talk within a group while also requesting that their identity is hidden from the other members of the group. This needs to be carried out while still transmitting their identity to the participating and controlling servers of the push-to-talk over cellular (PoC) system. The passing of identities allows the group to be monitored by authorised parties in order to discourage illegal activities from taking place while the users' identity is hidden.
It is the aim of embodiment of the present invention to address or at least mitigate the problems described above.